Sarah, I gotta agree with Nan that I wouldn't use "Andersen" for a girl, for the reason she cited. It's okay for a boy, tho. Actually, she suggested "Ander", but I believe the correct Scandinavian (Swedish?) version of Andrew is "Anders" (with the "s").
By the way, back in Cleveland we finally had Calvin bring the chips, I brought a watermelon (on the bus!), and we laughed about it afterwards.